, 

No, 87 

1959 

THE HICKORY RUN DEER EXCLOSURE 

The damage that deer can do to both planted and natural tree seedlings is vividly demonstrated by a l/l0-acre 

fenced exclosure at Hickory Run State Park in Carbon County, 

Pennsylvania. Here, by comparing the growth of trees that 

have been browsed by deer with the growth of trees that have 

been protected from deer by the fence, one can see the injurious effects of browsing strikingly revealed. 

HISTORICAL 

According to Park Superintendent John J. McGinley, 

the area where the plot is located had once been farmed, and 

is believed to have been abandoned at least 35 years ago. 

Very little woody vegetations grew up during the next 15 

years. The exclosure was then built (about 1938) to see 

whether better establishment and growth of the dative trees 

would occur under protection from deer. 

During the next decade, some scattered scrubby hardwoods, mostly gray birch and aspen, became established both 

in the plot and outside, but the stocking was sparse and 

spotty, In 1950, the area was planted to red, pitch, and a 

few white pines. The protected plot was planted with red 

pines at the same time and at the same spacing as outside, 

Today a number of the red pines planted outside the 

fence are dead and gone, and the survivors are misshapen and 

still short because of continued browsing by deer. Their 

average height is only 2% feet. In contrast, the protected 

red pines inside the fence are tall and well-formed; some 

are 17 feet tall and the average is 11 feet (fig, 1). Both 

pitch and white pines, which were planted only in the unprotected area, are even-shorter and more heavily browsed than 

the unprotected red pines, 
Figure I.--The small red pine trees on the right have been 

stunted by deer browsing; the large ones on the left have 

been protected by the fence. All were planted at same time. 

DAMAGE FROM BROWSING 

To' get a measure of the damage done by deer to both 

planted and natural trees, the trees were tallied by heights 

inside the exclosure and on an unfenced but otherwise similar plot nearby. All trees on the unprotected plot were recorded; inside the exclosure all pines were recorded but, 

because of the dense growth, only a 50-percent sample of the 

natural hardwoods was taken. Three large trees in the exclosure that apparently antedated the fencing were not tallied. The tally data are summarized in table l. 

As compared to the protected trees inside the exclosure, the trees outside have suffered substantially in 

both numbers and height growth because of deer browsing. 
Both timber values and aesthetic values have been severely 

damaged, 

Table 1.--Average number of trees per acre and average heights, 

by species, inside and outside the exclosure 

Stems per acre Average height 

Species 

Inside Outside Inside Outside 

Red pine 

White pine 

Red oak 

Black cherry 

Red maple 

Beech 

Bigtooth aspen 

Quaking aspen 

Gray birch 

Serviceberry 

Number Number Feet I 

1 I 

*None planted. 

DEER DESTROY OiYN FOOD SUPPLY 

Another result of severe browsing by deer is their 

tendency to destroy their own food supply. Their critical 

period is in the winter, when they must depend on woody 

browse for subsistence, An excessive number of deer in an 

area may consume the woody browse faster than it can grow in 

the summer, whereas fewer deer will permit an increasing 

amount of suitable browse to be produced, 

This is demonstrated on the fenced plot--more trees 

of all species (except white pine) were found inside the 

fence than outside. Some of these species, as well as certain shrubs, were not found anywhere outside the fenced plot. 

A better measure of available browse than number of 

stems, however, is the amount of twiggy crown within reach 

of deer, To measure this, woody plant crowns under 5 feet 

in height.were tallied on line-point transects both inside 

and outside the fence (table 2). (The percentages for the 

fenced plot add up to more than 100 because some crowns 

overlapped.) Outside the fence, 85 percent of the area had 

no woody plant cover under the 5-foot level, as compared to 

only 21 percent inside the fence, 

WHAT IT MEANS 

The tree growth inside this exclosure shows that, had 

there been no deer--or even substantially fewer deer--to 

browse in this area, the area could have been planted suc- 
Table 2.--Percent of total area under 5 feet high occupied 

by woody plant crowns inside and outside the exclosure 

Species Inside Outside 

Percent Percent 

Red pine 46 3 

Red oak 2 0 

Black cherry 1 * 

Aspen 9 0 

Gray birch 16 13 

Other tree species 2 * 

Willow (shrubs) 4 0 

Meadowsweet 2 * 

Blackberry 6 1 

Dwarf sumac 2 0 

Blueberry 16 6 

Bush-honeysuckle 4 0 

Wild raisin 1 0 

- 

*Observed but did not occur on sampling points. 

cessfully, or would have restocked to native tree species 

even without planting. The fact that the area outside the 

fence remains poorly stocked is incontrovertible evidence of 

an excessive deer population. 

Such excessive deer populations are generally recognized by foresters throughout Pennsylvania--and elsewhere-- 

as a common nuisance. And wherever they occur, as on the 

study area described here, regeneration of the forest is 

dramatically impeded and deer habitat continues to deteriorate. 

--TED J. GRISEZ 

Research Forester 

AGRICULTURE-FOREST SERVICE-UPPER DARBY